mmc: mmci: implement pre_req() and post_req()

pre_req() runs dma_map_sg() and prepares the dma descriptor for the next
mmc data transfer. post_req() runs dma_unmap_sg.  If not calling pre_req()
before mmci_request(), mmci_request() will prepare the cache and dma just
like it did it before.  It is optional to use pre_req() and post_req()
for mmci.

Signed-off-by: Per Forlin <per.forlin@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/mmci.h b/drivers/mmc/host/mmci.h
index 2164e8c..79e4143 100644
--- a/drivers/mmc/host/mmci.h
+++ b/drivers/mmc/host/mmci.h
@@ -166,6 +166,12 @@
 struct variant_data;
 struct dma_chan;
 
+struct mmci_host_next {
+	struct dma_async_tx_descriptor	*dma_desc;
+	struct dma_chan			*dma_chan;
+	s32				cookie;
+};
+
 struct mmci_host {
 	phys_addr_t		phybase;
 	void __iomem		*base;
@@ -203,6 +209,8 @@
 	struct dma_chan		*dma_current;
 	struct dma_chan		*dma_rx_channel;
 	struct dma_chan		*dma_tx_channel;
+	struct dma_async_tx_descriptor	*dma_desc_current;
+	struct mmci_host_next	next_data;
 
 #define dma_inprogress(host)	((host)->dma_current)
 #else